1. Field of the Invention
This invention relates to a recording and reproducing magnetic head to be used in a magnetic disc cartridge, and more particularly to a magnetic head of a straddle type.
2. Description of the Prior Art
Ordinarily, magnetic heads are classified into two types, one being a straddle type and the other being a tunnel type. The straddle type magnetic head permits the width of its I-shaped core portion to be wider than that of the tunnel type, and hence exhibits advantageous features of providing higher magnetic properties and higher output characteristics.
FIGS. 1 and 2 illustrate a conventional magnetic head of the straddle type. The magnetic head comprises a recording and reproducing magnetic core 1 made of a magnetic material such as ferrite and formed into two pieces forming a recording and reproducing gap 1a between the leg portions 1b.
The magnetic head further comprises two erasing cores also made of a magnetic material such as ferite, and arranged on both sides of the recording and reproducing magnetic core 1. Portions 3 made of a non-magnetic material such as glass are provided in combination with the erasing cores 2, respectively. A pair of core holders 4 made of a non-magnetic material such as a ceramic and formed with grooves 4a for receiving the erasing cores 2, respectively, are arranged on both sides of the recording and reproducing magnetic core 1 together with the erasing cores 2 in an opposite relation.
FIG. 2 illustrates, in a plan view, the arrangement when the members are assembled into the magnetic head. During the assembling, the erasing cores 2 are positioned with respect to the recording and reproducing magnetic core 1 so that erasing gaps 2a of a predetermined distance are maintained between the erasing cores 2 and the recording and reproducing magnetic core 1. After positioning of the erasing cores 2, the erasing cores 2 are secured in these positions by the use of a binding material such as glass.
The straddle type magnetic head ordinarily utilizes the recording and reproducing magnetic core 1 as one part of the erasing magnetic circuit. However, in the conventional magnetic head, the position of the recording and reproducing magnetic core 1 has been so selected that the recording and reproducing gap 1a opposes the central parts of the erasing cores 2 as shown in FIG. 2. As a consequence, a DC bias is caused by the erasing magnetic circuit to be applied between the right and left parts of the recording and reproducing magnetic core 1 through the recording and reproducing gap 1a, thus causing a peak shift upon generation of high frequency components. This tendency becomes conspicuous during a narrow track operation, and makes it difficult to operate the magnetic head in the narrow track and high-density recording state.